Gas turbine engines typically are formed from a compressor, a combustor positioned downstream from the compressor, and a plurality of turbine blades coupled to a rotatable disc positioned downstream from the combustor. The compressor receives air from an inlet and compresses the air before passing the compressed air to the combustor. In the combustor, the compressed air is mixed with fuel, and the mixture is ignited. The combustion gases produced in the compressor are passed to the turbine blades and cause the turbine blades to rotate. The combustion gases are then expelled from the turbine engine through an exhaust outlet at the rear of the turbine engine.
Some gas turbine engines use evaporative cooling systems to cool the intake air upstream of the compressor. Cooling the intake air improves the power and efficiency of the turbine engines and can, in some instances, reduce emissions of, for instance, NOx. Conventional evaporative cooling systems often include an array of nozzles positioned upstream of a compressor in an air intake duct. The nozzles are positioned to spray a cooling fluid, which is often water, in a downstream direction and generally parallel to a longitudinal axis of the duct. The nozzles often  produce a plurality of droplets having a Dv90 between about 25 microns and about 40 microns. Dv90 is a measurement of a drop diameter, whereby 90 percent of a total fluid volume of fluid is composed of droplets less than the measurement. For instance, one particular nozzle may consistently produce droplets having a Dv90 measurement of about 28 microns at a distance of 3 inches from the nozzle. However, at distances between 6 and 12 inches from the nozzle, the nozzle may produce droplets having a Dv90 of about 75 microns due to agglomeration.
Fine spray droplets have a tendency to agglomerate with each other while suspended in air and on surfaces. Agglomeration increases a droplet's overall size and reduces the amount of surface area relative to droplet mass, thereby increasing the time required for the droplet to evaporate. Using a simple evaporation model based on an evaporation rate being directly proportional to a surface area of a spherical droplet leads to a conclusion that the time necessary for complete evaporation of a droplet to occur is directly proportional to a diameter of a droplet squared. Using this model, the amount of time necessary for a droplet having a diameter of about 75 microns to evaporate is about 9 times greater than the amount of time needed for a droplet having a diameter of about 25 microns to evaporate.
Conventional turbine engines often do not have sufficient residence time in a duct upstream of a compressor to allow all of the droplets emitted from the array of nozzles to evaporate before entering the compressor. Thus, droplets often enter the compressor, which can cause erosion of various components of the compressor. Thus, a need exists for a more efficient evaporative cooling system for reducing the temperature of air flowing into a turbine engine while preventing at least a substantial portion of the droplets from entering a compressor of the turbine engine. 